[Analysis of the Nuchal Transparency (NT) Screening Concept at the Gynecologocial Clinic of MHH: a Prospective Follow-up Study]

Background: To date, various and partly competitive screening strategies for the risk calculation of trisomy 21 are applied in Germany. The aim of this study was to control the published test performance data of different methods in an unselected group of patients, thus allowing us to clearly assess the practical value of the respective methods.

Patients And Methods: At the MH Hannover, 744 women with a singleton pregnancy underwent an NT measurement according to the FMF guidelines. Additionally, 590 of these women had a PAPP-A and free ssHCG testing in a laboratory accredited by the FMF London. The fetal outcome of all 744 patients examined was assessed. Based on these data, test performance values were calculated for each test strategy under the hypothetical assumption that every women would have followed the same screening strategy.

Results: Age-related screening revealed to have the highest false-positive rate (25 %). Age screening combined with serum markers showed to have the highest sensitivity (100 %). Screening combining age, NT measurement and serum markers yielded the highest specificity (97 %). Combined screening by NT and age achieved the same sensitivity as age-related screening with a markedly lower false-positive rate than screening combining age and serum markers. Invasive tests were performed in 11 % of the patients. In 8 % of these, a pathologic karyotype was detected.

Conclusions: In comparison to age-related screening, first trimester screening allows us to define groups at risk for trisomy 21 more clearly. This seems to justify the clinical importance of this search strategy, and accordingly, invasive procedures are done less frequently in a higher proportion of younger women.